Aging effects on chemical transformation and metal(loid) removal by entrapped nanoscale zero-valent iron for hydraulic fracturing wastewater treatment
- Authors
- Sun, Yuqing; Lei, Cheng; Khan, Eakalak; Chen, Season S.; Tsang, Daniel C. W.; Ok, Yong Sik; Lin, Daohui; Feng, Yujie; Li, Xiang-dong
- Issue Date
- 15-2월-2018
- Publisher
- ELSEVIER
- Keywords
- Nanoscale zero-valent iron; Alginate entrapment; Hydraulic fracturing; Aging effect; Chemical speciation; Metal/metalloid removal
- Citation
- SCIENCE OF THE TOTAL ENVIRONMENT, v.615, pp.498 - 507
- Indexed
- SCIE
SCOPUS
- Journal Title
- SCIENCE OF THE TOTAL ENVIRONMENT
- Volume
- 615
- Start Page
- 498
- End Page
- 507
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/77344
- DOI
- 10.1016/j.scitotenv.2017.09.332
- ISSN
- 0048-9697
- Abstract
- In this study, alginate and polyvinyl alcohol (PVA)-alginate entrapped nanoscale zero-valent iron (nZVI) was tested for structural evolution, chemical transformation, and metals/metalloids removal (Cu(II), Cr(VI), Zn(II), and As(V)) after 1-2 month passivation in model saline wastewaters from hydraulic fracturing. X-ray diffraction analysis confirmed successful prevention of Fe-0 corrosion by polymeric entrapment. Increasing ionic strength (I) from 0 to 4.10 M (deionized water to Day-90 fracturing wastewater (FWW)) with prolonged aging time induced chemical instability of alginate due to dissociation of carboxyl groups and competition for hydrogen bonding with nZVI, which caused high Na (7.17%) and total organic carbon (24.6%) dissolution from PVA-alginate entrapped nZVI after 2-month immersion in Day-90 FWW. Compared to freshly-made beads, 2-month aging of PVA-alginate entrapped nZVI in Day-90 FWW promoted Cu(II) and Cr(VI) uptake in terms of the highest removal efficiency (84.2% and 70.8%), pseudo-second-order surface area-normalized rate coefficient k(sa) (2.09 x 10(-1) L m(-2) h(-1) and 1.84 x 10(-1) L m(-2) h(-1)), and Fe dissolution after 8-h reaction (13.9% and 8.45%). However, the same conditions inhibited Zn(II) and As(V) sequestration in terms of the lowest removal efficiency (31.2% and 39.8%) by PVA-alginate nZVI and ksa (4.74 x 10(-2) Lm(-2) h(-1) and 6.15 x 10(-2) Lm(-2) h(-1)) by alginate nZVI. The X-ray spectroscopic analysis and chemical speciation modelling demonstrated that the difference in metals/metalloids removal by entrapped nZVI after aging was attributed to distinctive removal mechanisms: (i) enhanced Cu(II) and Cr(VI) removal by nZVI reduction with accelerated electron transfer after pronounced dissolution of non-conductive polymeric immobilization matrix; (ii) suppressed Zn(II) and As(V) removal by nZVI adsorption due to restrained mass transfer after blockage of surface-active micropores. Entrapped nZVI was chemically fragile and should be properly stored and regularly replaced for good performance. (C) 2017 Elsevier B.V. All rights reserved.
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Collections - College of Life Sciences and Biotechnology > Division of Environmental Science and Ecological Engineering > 1. Journal Articles
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